東華大學圖書館 |

Evaluating New Methods to Detect Threatened and Cryptic Manatee Populations.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Evaluating New Methods to Detect Threatened and Cryptic Manatee Populations./
作者:	Farinelli, Sarah.
面頁冊數:	1 online resource (178 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
標題:	Ecology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30488527click for full text (PQDT)
ISBN:	9798379721169

Evaluating New Methods to Detect Threatened and Cryptic Manatee Populations.
Farinelli, Sarah.

Evaluating New Methods to Detect Threatened and Cryptic Manatee Populations. - 1 online resource (178 pages)

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Thesis (Ph.D.)--George Mason University, 2023.

Includes bibliographical references

The conservation status of approximately 21% of marine mammals has not yet been assessed, despite the vast number of anthropogenic threats they face at local, regional, and global scales, with the primary threats being bycatch in fisheries, pollution, and illegal hunting. Several factors make detecting marine mammals exceptionally difficult in comparison to terrestrial mammals, including cryptic behavior, such as long dive times and poor water clarity. Furthermore, anthropogenic threats can exacerbate cryptic behavior of marine mammals. Manatees (Trichechus spp.) are examples of marine mammals that are considerably difficult to detect, especially where these species are still illegally hunted, due to their cryptic nature and ability to inhabit heterogenous aquatic environments. Currently, aerial surveys are the predominate method for monitoring manatee populations (as well as other marine mammal populations such as cetaceans). However, due to safety and logistical concerns, many manatee populations are not able to be routinely surveyed as is the case for African manatees (T. senegalensis). As a result, existing methods to detect marine mammals may not be sufficient to accurately survey populations to obtain information critical to establishing effective conservation efforts. The main goal of this dissertation is to evaluate two new methods that stem from advancements in technology to detect cryptic manatee populations: 1) the use of unmanned aerial vehicles (UAVs) and 2) environmental DNA (eDNA) from residual saliva remaining on foraged upon aquatic vegetation. To do so, I first performed a comparative analysis of existing methods (indirect observations as proxies for manatee presence and boat-based visual observations) with the use of a small, multi-rotor UAV to detect African manatees in two lagoon waterbodies in southwest Nigeria where the species is still heavily hunted. I measured environmental variables hypothesized to affect manatee presence at a survey site and associated these variables with detection methods. Finally, in this study, I also used the UAV to monitor real-time threats to the species at the survey sites. The results of this study showed that the indirect observation method results in the greatest number of detections, but UAV surveys resulted in twice the number of detections in comparison to boat-based visual observations. Water depth was the most influential variable associated with detecting African manatees using a UAV and with indirect observations, although the direction of the effect differed between the two methods. Using the UAV, the most abundant threats to African manatees that were observed included the presence of fishermen and fishing nets. In the second study, I further evaluated survey effort associated with conducting UAV surveys to detect Amazonian manatees (T. inunguis) in a controlled environment at a closed man-made lake being used to rehabilitate a known number of individuals and evaluated the effect of various environmental variables on detection probability. In this study, I was able to calculate the number of repeat surveys (n = 3) to be confident that true abundance was established using a UAV. I also found that environmental variables influencing behavior of individuals (i.e., water temperature) had the greatest effect on detection probability in comparison to habitat use or environmental variables associated with visibility within the water column. This is the first time a UAV has been used to detect either species. Finally, the third study conducted aimed to determine the efficacy of using residual saliva remaining on foraged upon aquatic vegetation, a new source of eDNA for aquatic species. I collected ex-situ eDNA samples by hand-feeding captive Florida manatees (T. m. latirostris) kale and from collecting recently foraged upon water lettuce (Pistia stratiotes) from the captive Amazonian manatees in the second study. I also collected eDNA samples from water hyacinth (Eichhornia crassipes) and various grasses (Brachiaria spp.) hypothesized to have been foraged upon by wild African manatees at the study sites in Nigeria from the first study. I successfully detected manatee eDNA for the first time from vegetation samples across all study sites. Overall, this dissertation resulted in protocols developed for two new survey methods to detect cryptic manatee species in difficult-to-detect environments. Continued evaluation of these methods has the potential to develop range-wide surveys to better inform management of understudied and threatened aquatic species, such as manatees.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798379721169Subjects--Topical Terms:

516476
Ecology.
Subjects--Index Terms:

Environmental DNAIndex Terms--Genre/Form:

542853
Electronic books.

Evaluating New Methods to Detect Threatened and Cryptic Manatee Populations.
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